FACILITATED DIFFUSION

• A type of passive transport that does not require energy to move molecules down their concentration gradient

• uses membrane proteins to move molecules across the membrane that are large or charged (ions)

How does active transport differ from diffusion?

Active Transport• Moves molecules from low

concentration to high concentration• Requires energy in the form of

ATP• Used to generate impulses

through nerve cells & to allow cells to continue to store nutrients

Bulk Transport-Endocytosis

• Cells ingesting (taking in) large particles, fluid, etc.• Membrane folds inward, makes a pouch, encloses material, and

membrane pinches off• Material is enclosed in a vesicle• Transported to lysosome for digestion, or to other organelles for

use (ex. WBC take in & destroy bacteria)

Types of Endocytosis

• Pinocytosis: solutes or fluids (cellular drinking)• Phagocytosis: large particles, cells (cellular eating)

Bulk Transport-Exocytosis

• Reverse of Endocytosis• Vesicles fuse w/membrane, releasing

contents• Ex: releasing proteins like insulin (

animation)

IMPORTANT!!!• Active transport & ALL forms of

Bulk transport require energy!

Can you???Distinguish between passive and active

transportExplain why facilitated diffusion is a

type of passive transportDescribe the difference between a

hypertonic, hypotonic and isotonic environment

Compare/Contrast endocytosis and exocytosis

Describe the structure of the cell membrane & a phospholipid